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  1. #26
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    Last edited by Tohot; 12-08-13 at 05:54 AM.

  2. #27
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    Bumping up

  3. #28
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    Quote Originally Posted by Tohot View Post
    Bumping up
    Sorry it took until now to get back to you, I've been busy and fighting the weather (which can more then double my commute and supply run times cutting into my free time) the end of this last week.

    3. ----- In my experience an e-bike throttle is pretty much an e-bike throttle and its just a matter of getting the wires hooked up to the controller correctly. There are exceptions of course I'm sure but so far I haven't had a problem and just buy whatever throttle assembly I like the feel of and hook it up to the controller, at least with an e-bike controller and an e-bike throttle. Now if you start using RC controllers then things get more interesting since they aren't designed to use e-bike type throttle but I doubt you would even consider doing that.

    2. & 3. ------ The main two things that you need to make sure are compatible [besides voltage and wattage (or amps instead of wattage)] are Brush-less vs. Brushed and Sensor-ed vs. Sensor-less motors and controllers come in both variations and need to match. Either it is a Brush-less motor or a Brushed motor (all of the motors I have seen you look at so far are brush-less ones) and you need to use the controller type to match.

    ----- A brushed motor will have only two big thick strong wires and a brushed controller will have the same two big thick strong wires to match for the motor plug on the controller. I have never seen a brushed motor with sensors, they is no need for them on a brushed motor.

    ----- A Brush-less and Sensor-less motor will have only three big thick strong wires and a brush-less brush-less controller will have the same only three big thick strong wires to match for the motor plug on the controller.

    ----- A Brush-less and Sensor-ed motor will have three big thick strong wires plus a few smaller thinner wires for the hall sensors inside the motor and a brush-less sensor-ed controller will have wires to match both three big and a number of small ones for the sensors.

    ----- There are Brush-less motor controllers out there that will work as either a sensor-ed or sensor-less controller and you just don't hook up the sensor wires when using a sensor-less motor and you have to either flip a little switch or twist two of the sensor wires together on the controller to tell it you are running sensor-less.



    The motor you linked too judging by its picture appears to be a brush-less sensor-ed motor because I see three big wires and a few small mires coming out of it in the picture. Provided the picture is accurate and not just a generic picture they put on the listing that is what it is even though it doesn't say so specifically in the listing.

    For the motor controllers you linked too. The top one you linked too is a brush-less sensor-ed controller which matches what you need for the motor you linked too. But the bottom one you linked too is a brushed motor controller, it will not work with a brush-less motor. Also, the top one you linked too has a 13-Amp limit (+ or - 1) on 48V which is a little high for the size of motor you want to run with it but short of a much more expensive programmable controller you are probably not going to find much lower then that so I say go for it especially since you are finding it hard to find a 48V controller for your set-up. Just be careful to not bog the motor down for a long time while climbing a big hill and not pedaling or something like that (more explanation on why not below on my response to chvid's post).

    Quote Originally Posted by chvid View Post
    Tohot, you seem to have the misconception that the nominal power rating of a motor has anything to do with how much power it can put out <at least for a short time>. A "500 watt motor", can easily put 1500 watts given the right controller. In fact in can put a great deal more power than the nominal rating until it burns out from heat, the controller amp limit is reached, or the battery is trashed from a too high amp draw, exceeding the C rating of the battery. So plugging in the voltage of the battery into Ohm's law, as a way of calculating some "operating amperage" of the motor is quite useless. The amperage varies continuously as the motor operates, spiking to very high levels, say 40 amps, when torquing the motor at a stop sign with no pedalling. The nominal rating is also useless other than an extremely rough guide to the power of the motor. For example, my Conhis motor (same as a Golden motor Pro hub) is a so-called "500 watt motor". My Cycleanalyst routinely shows power over 1300 watts on this motor, given the 30 amp controller I use, and the 48V Headway pack I use. This is confusing to the newbie. That motor could probably produce over 2000 watts, if the phase wires were upgraded, and a high powered controller was able to push 50 amps into it. Another example: my Cute100 geared brushless motor is a "250 watt motor". I usually see many spikes to 700 watts on this motor (as seen on CycleAnalyst), with a 15 amp limited controller and 48V Headway. I wouldn't put any more than 750 watts into it though, on a continuous basis - the gears would be at risk inside the motor. There is also further refinement of the power issue when it comes to "phase amps" vs "battery amps"...can't say I know enough to untangle those concepts. The CA measures battery amps.
    Yes, chvid, is absolutely correct here that the controllers maximum Amp limit is often what truly limits the maximum amount of power the motor is allowed to use. The wattage rating on a motor is how much power it can be allowed to continuously run at for extended periods of time under normal usage conditions and not hurt the motor. It is possible for a motor to pull larger amounts of power for shorter periods or under specific conditions. I say "pull" because an electric motor is unique compared to many other motor types in that it actually pulls from the battery as much power as it needs to get the job done within certain limits of its design if it is allowed to do so and the controller doesn't "put it on a diet" and limit the maximum it can pull. Put a motor that is only designed to run on 250-watts continuously under conditions where it has to pull a 1,000-watts to do the job it is being asked to do and if the voltage is high enough and the internal wire windings on the motor are thick enough so as to directly prevent it from physically doing so then it will do so if the controller doesn't limit how much it can draw and if this condition is allowed to continue long enough the motor will literally burn itself out trying to do a job it isn't big enough to do.

    Electric motors are very good employees, no matter how big of a job you give them they will try their best to do it even if they are going to burn themselves out trying which is why you need to give them a boss (the controller) that is smart enough to not give them more then they can handle for too long. This is where the maximum amperage setting of a controller comes in, most controllers its just a set number that is hard wired into the controller. The top controller you linked too that is 16-Amps at 36V and 13-Amps at 48V which is actually a pretty good low limit to find on a controller to use with a smaller motor like you are looking at using. More expensive and complicated programmable controllers will actually let the use adjust this setting (along with other settings) by plugging a cord between the controller and their computer with the right software on their computer.

    A 13-Amp (+ or - 1) top end limit on 48V means that the controller will jump in like a good boss would and keep whatever motor you put on it from pulling anything more then 624-watts (+ or - 48-watts) even if the motor needs more to do the job it is being asked to do which isn't a bad choice on a motor rated to do 250-watts continuously under normal circumstances. Me personally I would prefer limiting down to more like 400-watts (approximately an 8-Amp limit) or so which would make it almost impossible to burn out the motor by asking it to do too much but so long as you don't try to make the motor do a big job all by itself for a long time (like climbing a big long hill and letting the motor do all the work and not pedaling at all yourself) that should be a pretty good ultimate top end limit for the size of motor you are wanting to use.

    The "Cute100" motor that chivid is using is exactly the kind of motors you have been looking at and linking too so his experience with his and that it occasionally pulls a quick spike all the way up to 750-watts for a short period of time when put under a lot of load and this has not hurt his motor (or at least not that he has noticed) and that the controller he is using has a 15-Amp top limit says that using the controller you linked too with a 13-Amp top limit should work pretty good for you as well.

    What he says about the "C" limit of the batteries is also true. If you have 10-Amp batteries with a "C" limit of 2 that means 2x10=20 is the maximum amount of amps you can pull from the batteries continuously under normal circumstances without hurting them, again occasional spikes that go higher but for very short periods of time can be even higher but you can't do more then that continuously without hurting the batteries. Most battery suppliers will list the regular continuous "C" limit number. A few ones with better documentation will list other "C" numbers such as the 5-minute, 1-minute or 10-second "C" limit number. For example one of my favorite batteries is a particular 20-Ah LiFePO4 prismatic cell I get for a good price from one supplier that has a C=2 rating for continuous use, C=3.5 for 5-minutes or less and a C=10 rating for 10-seconds or less so I know it can take spikes all the way up to five times the normal for very short period of time and can do almost double for a full five minutes without damage if necessary.
    Last edited by turbo1889; 12-08-13 at 01:51 PM.

  4. #29
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    Quote Originally Posted by turbo1889 View Post
    .
    Quote Originally Posted by chvid View Post
    .
    wow thanks that is a loooong post
    you should check https://www.youtube.com/watch?v=Z-VLdE6RxYQ ,im planning to buy toshiba 11.1V 12 cells laptop batteries,they look like truth ,cheap light,high capacity etc...
    (im planning to go 15x2 of those 3.7V batteries)

    Yeah pedaling...there will be no pedaling(its like a mini scooter) which is kind of a problem , but there is maybe just 50m slight hill and that is all in 3 km with 1-6 stops
    well if it could take 3 minutes of full power if would be fine...
    is it enough that i stop power when i notice i reached high speed or to much hill?



    what about this brick guys ?
    http://www.ebay.com/itm/60V-350W-Bru...1a56f7&vxp=mtr
    worse or better?
    Last edited by Tohot; 12-09-13 at 06:35 PM.

  5. #30
    Transportation Cyclist turbo1889's Avatar
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    Top speed usually isn't an issue as far as overheating a motor unless your running it way over specs. Its when you bog it down on a long hill and just keep the throttle pinned at full that starts to overheat motors.

  6. #31
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    Quote Originally Posted by turbo1889 View Post
    Top speed usually isn't an issue as far as overheating a motor unless your running it way over specs. Its when you bog it down on a long hill and just keep the throttle pinned at full that starts to overheat motors.
    Hi,long time no RE

    For now i got the throttle and toshiba laptop batteries,they seem to have 2600 mAH as written
    and those are 12 x 18650 3.7V Rechargeable Lithium Li-ion Batteries
    and iīve read that they can go 30 Amps no problem so i do not need to take like 2x13 of them,just 13 and will not burn out ?? (someone told me i should take double so it cant burn)
    I will take more time to learn about electronics..... but anyway... if this motor takes 10 Amps or more will it than spend more watts and is it common or just on a hill or something?? (btw im thinking about 10A X 48V = 450W)

  7. #32
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    30 amps on a 2600mAhr laptop or Trustfire or some such? That's over 10C! Those batteries won't last more than a week, if that...you'll need a much larger can like a 12x 10Ahr Headway, at 3C, to put out 30 amps. Remember, each cell will be asked by a 30 amp controller to put out 30Amps!, you don't add the amps of each one,when they are in series. You could put out thirty amps maybe if they were in parallel, but then you'd be running at flashlight voltage. You might be good for a few miles before they reach 50% discharge..and give up the ghost operating WAY above their C rating...There's a good reason the average ebike pack weighs 10 lbs or more...you need that much lithium to "not get stressed" by the amps requested. You might as well bite the bullet and buy something decent like a 48V 10Ahr Ping battery which would be happy at 15Amps continuous, most of the time under 5amps. Otherwise its a waste of money and time.
    Last edited by chvid; 01-08-14 at 10:04 PM.

  8. #33
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    can someone tell me the max discharge current of li-ion 18540 3.7v battery,i searched but its hard to even find the max current and its not always the same value(is every li-ion same??),and how much current can 250w 48v engine make ?? and im not sure what C means is it equal to A(amps) ?
    for example :
    Specification
    Rechargeable Li-ion Power Battery Cell
    High power battery cell

    High temperature resistance PET

    Technical Parameter
    Model: 18650
    Material: Li-ion
    Voltage: 3.7V
    Capacity: 1300mAh
    Discharging rate:
    * Nominal discharge capacity: 1300mah (300mA, 2.5V discharge)
    * Standard discharge capacity: 1250mah (10A, 2.5V discharge)
    Standard Charge: 1C at 1.3A
    Maximum continuing discharging current: 10A
    Dimension: Height 65 mm, Diameter 18 mm
    Weight: 42g

    http://www.ebay.com/itm/HID-Battery-...-/320920557168
    P.S.
    I sux at this

    and if its 10 A at 2.5v is it better to use something like 80v battery pack for 48v discharge ?
    Last edited by Tohot; 01-09-14 at 05:06 AM.

  9. #34
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    The battery you indicate on ebay is apparently rated at around 8c continuous, so you could possibly pull 10 amps out of one of them, continuously, since it is a 1.3 Amp Hour battery (1300 mAhr). That's way more than most laptop batteries. If the rating is accurate, of which many are overstated. The more you put in series, to get the desired voltage, you will still be putting out 10amps, at that voltage. I'm skeptical of that rating though.

    "C" rate refers to the amperage of the discharge in comparison to the size of the battery...

    A 10 AmpHr battery subjected to a 1 C discharge rate will be empty in one hour, emitting 10 amps over that period.
    A 10 AmpHr battery subjected to a 10C discharge rate (100 amps) will be empty in 6 minutes, emitting 100 amps over that period.

    The C rating of the battery is "what is the maximum discharge rate (C)" that the battery will be happy with.
    If the 10Ahr battery in the example was rated at 2C, it could "happily" put out 20 amps for 30 minutes, before it was empty.
    If it tried to do 100 amps (because a controller asked it to) it would be empty in six minutes, and its health would also be compromised.
    Last edited by chvid; 01-09-14 at 08:32 AM.

  10. #35
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    thank you i think i get it now so if battery has 10Ah and 4C its (10x4)Amps discharge for (10/(10x4))h

    i have these 12 batteries 18650(GRADE A) so i think its 4 Amps max discharge http://www.ebay.com/itm/350854439665...84.m1497.l2649

    Anyone know Max Amps that will 250w48v motor pull ? and when...

  11. #36
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    With my controller, a Cute 100 (nominally a 250W motor), at 48V, it will put out about 700watts, as my controller has a maximum amperage it can supply of 15 amps. (Ignore the 250 nominal - it doesn't tell you much). 50V*15Amps = 750 watts. That is at full throttle. Most of the time I will only be pulling a few amps or less, with a bit of throttle, holding my speed on the flats, say 100 or 200 watts. So that cruising wattage is about what the motor "is rated nominally". But on hills, and accelerating from a stop, the wattage will be much higher than the nominal 250watts. You could go higher than a 15 amp rated controller, but it would burn out the gears if it ran with that for a short period of time.
    Last edited by chvid; 01-09-14 at 12:56 PM.

  12. #37
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    1.)
    if i lock the throttle on lets say 50% is it possible that the engine will never pull more than 10 amps,(i wonder if locked throttle can be like a custom controller
    • This 48 volt controller has 13 connectors
    • Rated Voltage 36V / 48V
    • Rated Motor 250W / 350W
    • Rated Current 16ą1A
    • Conversion Efficency 95%
    • Under Voltage Protection 31.5-42V (ą0.5V)
    2.)
    Charging batteries:
    I am planning to charge them on 12V input with adjustable resistor to set at 4.1V, is it correct that if i put 1 or 10 or 100 batteries in parallel it will not burn the wires but just charge slower ?
    (i did charge 3 in series but not tried this jet,and btw computer shut down if i make changes when turned on,i guess its some safe mode and batteries wold run some added fans if plugged)
    I t was connected to my computerīs MOLEKS....
    3.)this is for later but what do you guys think about the idea of adding an extra battery for voltage drop,so if i have 48.1 voltage and it drops could i switch on the extra battery so i have extra duration or maybe just put 51.8 all together
    4.)i am thinking about putting my batteries on air so do you guys think it could help battery life ? (i think this could REALLY help,will need some anti water coating + Sun protector, idea is that air flows trough them as you ride (in some cube full of nets,similar to 3D led cubeīs structure! )
    P.S. if you find this interesting i could put some drawings
    Edit:
    Last edited by Tohot; 01-10-14 at 02:14 AM. Reason: sun,rain and all the weather poop i now am awere

  13. #38
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    Quote Originally Posted by turbo1889 View Post
    .
    Quote Originally Posted by chvid View Post
    .
    ? : D

  14. #39
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    @ Tohot

    I'll take that last post of yours as asking for a reply from me. Sorry, I've got an appointment I'm already late for and I've got to get on the bike and get moving and get into town, I'm already running slightly late. I'll try to get back to you on this later tonight, probably about 8-10 hours until I'll be back home and can read your updates and post. Just putting this quick post letting you know I'm still around and got the e-mail letting me know there has been some recent activity again on this thread. Just don't have the time at the moment to read, digest, and respond, will do so when I get back.

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    okay , not to worry : )

  16. #41
    Transportation Cyclist turbo1889's Avatar
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    Okay, a bit longer to get back to you, I ended up spending the night in town at a friends place, and just now and getting up on this lazy Sunday morning and using her computer to respond to your thread here:

    Quote Originally Posted by Tohot View Post
    1.)
    if i lock the throttle on lets say 50% is it possible that the engine will never pull more than 10 amps,(i wonder if locked throttle can be like a custom controller . . .
    Yes, and No. Reducing throttle does have some effect on how many amps can be pulled by the motor but only as a fractional limit of the motors own internal resistance and has far more effect on the motors RPM very similar to how voltage rather then amperage effects motor performance. Throttling in modern electric motor control circuits is done by square wave pulse modulation. That's a fancy way of saying the controller turns the power to the motor on and off really fast (as in thousands of times a second) so fast that there is no bumpy feel or any perceptible pulsing. At 100% throttle the power is on all the time and off none of the time (most controllers never do a true 100% but just slightly under). At 50% throttle the is on half the time and off half the time in this really fast on/off switching. At 90% throttle the power is on 90% of the time and off 10% of the time, etc . . . you get the idea. This is actually one of thee most effective and efficient ways to control the speed of a motor with very little wasted energy. So at 50% throttle the motor is on half the time and off half the time and the controller is switching between so fast you never feel or notice it. While the motor is on it can pull as many amps as it needs to provide the wattage to do the job it is being asked to do up to the maximum possible amperage allowed by the motors own internal resistance.

    The internal resistance of a well designed efficient electric motor is incredibly low and many of them of the size used in e-bikes if the internal resistance of the motor itself was the only limit on amperage are capable of drawing amp levels in the high double digits to low triple digits !!! Lets say for example that the motor you use was theoretically capable of pulling up to 40 amps if its internal resistance was the only limit on its amperage draw. If put under a heavy enough load and with the throttle "locked" to a maximum of only 50% throttle that means for half the time it was on it would be drawing 40 amps and the other half of the time it was off due to the throttle setting being done through this square wave pulse modulation technique it would be drawing zero amps. Since a modern motor controller pulls a steady constant stream of power from the battery and stores up little chunks of power for these short bursts that means that half on at 40 amps and half off at zero amps to the motor at 50% throttle pulls a steady stream of 20 amps from the battery to the controller.

    That is the only way throttle setting limits amps, otherwise all it does is control speed. Locking the throttle at 50% just basically has the effect of making the motor spin half as fast and any reduction in amps is a secondary effect not a primary one and is due to the amps limiting effect of the internal resistance of the motor which is not something your going to find on very many motor spec sheets and is usually something you have to calculate for yourself.

    The Amp limiting process inside a modern controller is a totally different system that works by a totally different method and has minimal effect on motor speed and just limits the maximum amps and any speed limiting effect is due to the load on the motor.

    For your kind of set-up your going to want to stick with as low of an amp limit on the controller that you can get all the way down to about 6-7 amps or so. I wouldn't go lower then that but you'll be lucky to find a 48V controller with an amp limit circuit of 10 amps much less anything lower so going too low is a pretty mute point for your build.

    If you have already bought the one with a 16 amp limit well that's what you have to work with. Build your battery C rating and number of cells in parallel to handle up to whatever the amp limiting circuit on the controller is and then you can be sure your battery is safe, no limiting of the throttle necessary.

    . . .

    2.)
    Charging batteries:
    I am planning to charge them on 12V input with adjustable resistor to set at 4.1V, is it correct that if i put 1 or 10 or 100 batteries in parallel it will not burn the wires but just charge slower ?
    (i did charge 3 in series but not tried this jet,and btw computer shut down if i make changes when turned on,i guess its some safe mode and batteries wold run some added fans if plugged)
    I t was connected to my computerīs MOLEKS....
    3.)this is for later but what do you guys think about the idea of adding an extra battery for voltage drop,so if i have 48.1 voltage and it drops could i switch on the extra battery so i have extra duration or maybe just put 51.8 all together
    4.)i am thinking about putting my batteries on air so do you guys think it could help battery life ? (i think this could REALLY help,will need some anti water coating + Sun protector, idea is that air flows trough them as you ride (in some cube full of nets,similar to 3D led cubeīs structure! )
    P.S. if you find this interesting i could put some drawings
    Edit:
    Yes, single cell voltage charging all in parallel your limits on how many cells you can charge at any given time is pretty open. There is a minimum number of cells you can charge in parallel so you don't try to charge them too fast. Obviously if your charging system won't charge one cell by itself too fast then your minimum number in parallel to safely charge is one cell, not a problem. There is also a maximum limit to how many you can charge together in parallel due to battery internal resistance. If you get enough of them in parallel on a small enough charger all the power of the charger is used to overcome the batteries internal resistance because you have so many of them it overwhelms the charger. Usually there is a very large gap between the minimum number and maximum number of cells that can be charged together in parallel. Just letting you know there is a limit on both ends. If you build your charger so that it charges a single cell as fast as it can be safely charged then usually you can do up all your cells in parallel on the same charger without reaching the upper limit and overwhelming the charger. I'd have to know the exact internal resistance specs. of your cells compared to their capacity to tell exactly how many that would be but it would really surprise me if you can't handle at least 20+ cells in parallel charging on a single cell fast charger built to charge a single cell as fast as safely possible.

    As to battery cooling, yes, air cooling as you describe does work and is better then just bunching the cells altogether and shrink wrapping them. But heat sink cooling works even better. Aluminum being one of the best heat sink materials If you take a solid bar of aluminum that is just a little less thickness your cylindrical battery cells are tall and drill rows of holes in it the same diameter as your cells and fill all the holes with cells and then wire them together that keeps them even cooler since the heat transfer from the cells to the aluminum block they are mounted in works better and moves more heat faster then air. Of course once you have the heat in the aluminum block you then have to get it into the air from the aluminum somehow. Cutting cooling fin like slots in the edges of the aluminum block is one option another is with an aluminum bike frame you can aluminum weld the aluminum block right to the bikes frame (before you put the batteries in it !!!) and then your entire bikes frame becomes a heat sink cooler for you bikes battery pack.

    I doubt though you'll have to do anything more drastic then open air cooling with space between the cells for air to flow, I have seen some builds though that went all the way with the aluminum block heat-sink approach.

    Liquid cooling is theoretically also possible if you can find a non-electric-conducting liquid that won't hurt the pack or wires. I've heard that pure green anti-freeze without any water added can be used but haven't tried it myself.

    I personally have never had any need to get more drastic then some limited application of the aluminum heat sink. I've got one "hill climber only" build that is powered by RC flat packs concealed in a bike bag (stealth build so no one knows its not just a pedal bike unless they look really, really close and know what to look for) where I put 1/8" thick aluminum plates between the thin flat packs before I shrink wrapped them together with the ends of the plates sticking out an inch or so on two sides as cooling fins.

    You should be just fine with air cooling, first thing that came to my mind was capturing and sealing the ends of your cylindrical cells in two flat plastic end plates with the centers of the cells exposed like little pillars between the plates and mounted so that air flows through that gap between the end plates when your moving.

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    Thanks for explaining all that,from your friends computer : D
    Damn,you know a lot about this things

    Yes,I already bough the 16 amp controller
    1. Tested my li-ion batteries and i guess the can take 5A no problem and 8.5A for some time (there was no C rating),They have 2600 mAh 3.7V so i used 3 in series each time
    a)60W12V(5A) Peltier Cooler + 2 X 21W12V(1.75A) Bulbs = 8.5A,that was for a long time so 2/3 batteries died either from heat or over-discharge that i was not aware of (apparently if li-ion is discharged to about 2V it is irreversibly damaged :/,i was able to barely hold them so i guess it was "Tohot" : D,i did read they can go 75 °C so i let them discharge anyway.
    b)This time i just had the 5A Peltier and new batteries had a very small increase in temperature,maybe like 10 °C i donīt know...
    2.) (conclusion)
    I will go for 39 cells 13x3 and that is about 1.6 Kg for 7.8Ah
    3.)What would be the tolerance of voltage to 48V motor ??
    4.)If i charge 1 battery on 12V is it enough to have a resistor and limit the current or do i really need to have 4V power source ?
    5.)Iīve red that li-ion should be charged to about 4V (depends on what you need) but dont all mobileīs 3.7V li-ions charge on USBīs 5V,is it damaging them and if not could i put my 18650 3.7v li-ions ? (or its probably another type of li-ion)
    6.)cant find this one out either....,tried to search for circuit but no use....,is ebikeīs brake just a normal bike brake with on/off switch inside that is connected to the controller?,i want to know if i could make my own brake with switch or is something in there (not just on/off switch)
    7.)would like to know if this is correct,a power source sends Volts but Amps can only be sent if requested from a loader,and if loader is working on 3v and source on 6v it will "ask" for double amount of amps because its actually requesting amps per volt and that would be why teaser guns need a lot of volts to get enough amps "requested" and so amps are the only thing that can actually burn you ?

    8.)and i want you to correct me if im wrong about this:
    I have a 10A Amperemeter http://www.ebay.com/itm/390630340679...84.m1497.l2649 so i guess i could put it in series with one group of batteries so i get only 1/3 of total current so i donīt burn it
    Last edited by Tohot; 01-15-14 at 12:06 PM.

  18. #43
    Transportation Cyclist turbo1889's Avatar
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    If they can take 5A per cell with no problems then your plan of using 3 cells in parallel by 13 in series sounds good to me (13s3p configuration).

    As to charging, I've never tried to build a variable resistor charger like you are doing, I've just always used a charger or power supply circuit that provided my desired voltage straight out. Can't say it wouldn't work, but can't say it would either since I haven't done it. I've done a lot of parallel charging but I always used a charger/power-supply at the desired voltage instead of trying to use a variable resister like you want to do to step down a little higher voltage source. I always just matched to the desired voltage.

    As to voltage tolerance range an extra cell or two won't cause problems with the motor usually, it's the controller that dictates that, does it have an absolute max voltage rating printed somewhere on the outside of the case? and if not then does the outer shell cover easily unscrew so you can read the max voltage rating on the side of the big capacitors? That is usually your top end limit since when stepping up the voltage beyond specs its usually a capacitor that you blow as the weakest link inside the controller as far as increased voltage is concerned. For example, I've seen 60V rated controllers that if you pulled the outer casing off of them the big capacitors on the inside (fairly obvious since they are one of the largest physically sized components often large round cylinder shaped) were rated for a max of 80V and that explained why people were getting away with running those controllers a little hot without problems. Always be extra careful when doing something like this and opening a cover to check the guts on a controller for stuff like this. And it's always the peak top charge voltage of your cells you compare to what the capacitors are rated for.

    If you get lucky you might find capacitors inside your 48V controller that are rated for a little over 60V peak which means you could use 45-cells to build your pack in a 15s3p configuration consisting of five seperate 3s3p partial packs that could be charged direclty off of your 12V power supply reaching a peak "fresh hot off the charger" voltage of 4V per cell which would make for 60V "fresh hot off the charger" which would drop down to a normal voltage of about 55.5V after the first couple minutes of use and would make charging easy as well charging the cells in strings of three in series straight off the 12V power supply you have. Obviously that would be running the controller and motor well over design specs, the motor would probably take it, the big question mark would be whether the controller could, might and might not. It would be a risk and a calculated gamble. Less of a risk and gamble if you could confirm that the capacitors inside the controller were rated for a little over the 60V "fresh and hot off the charger" voltage that would be put out for the first couple minutes of use until the cells settled down to their nominal voltage in use. I'm not sure I would take that kind of a risk and attempted over volt "hot rodding" of the system on a first build especially. It's just you asked so that's my thoughts on it and I personally wouldn't even attempt going more then one cell over voltage without checking the capacitor ratings on the inside guts of the controller.

  19. #44
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    Quote Originally Posted by turbo1889 View Post
    (Just so you get notification)
    Will check when it arrives!
    will try some hardcore cooling but later with 26 batteries,i would use small water balloons if in a need of protecting the cells
    Last edited by Tohot; 01-26-14 at 03:54 AM.

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    Quote Originally Posted by turbo1889 View Post
    If you get lucky you might find capacitors inside your 48V controller that are rated for a little over 60V peak
    controller inside.jpgcontroller outside.jpg
    Got it today,single 1000uF 63V Capacitor ,i hope not re-pasting will not cause a problem

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    Greetings fellow BikeForum Members
    Some questions again for 48V250W motor...
    1.Could 17A limit on 48V/350W Controller burn my motor since the amp limit is 15A (if so how much seconds would it take?)
    2.If so can i use a 15A fuse to protect the motor and witch one would it have to be ? (cannot find 48V fuse)
    3.Any way to make modifications to the " the controller ?(yes i am stuck with this controller ...)
    Last edited by Tohot; 02-26-14 at 01:51 PM.

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